Assassin's Creed 4: Black Flag lead designer Jean-Sebastien Decant told Polygon that Ubisoft makes a "master version" of each game in the franchise and PC is always the last to be developed – hence each iteration is delayed on the platform.
Explaining why the PC version is delayed Decant said:
"It all depends on what is the master version. If for instance, the [Xbox 360] version was the master version, or the PlayStation 3 version was the master version, then we'd need a little bit more time to adapt it for the PC. But we need to finish that other version first."
He added that because the PC version is the last to be developed the team needs an extra few weeks to ensure that the final product is highly polished.
For Assassin's Creed 4: Black Flag, Decant said there are two master versions. He revealed that both the Xbox 360 and PS3 SKUs were developed simultaneously on the Anvil game engine which was pioneered in Assassin's Creed 3.
"The technology goal we had was for the current-gen," Decant said. Once this was done Ubisoft turned its attention to the PS4 and Xbox One; and PC editions. "You need to finish one and make sure that it's clean before you can then finish the others."
You can check out the lastest trailer for Black Flag and read up on our recent interview with the game's director, Ashraf Ismail.
Assassin's Creed 4 was confirmed this week to be releasing on November 19th on PC. It will be hitting PS3, Wii U, and Xbox 360 on October 29th in North America and November 1st in Europe. Black Flag is set to launch on PS4 on November 15th in North America and November 29th in Europe.
The Xbox One edition will be launched on November 22nd.